Single phase watthour meter



Sept. 27, 1960 F. KURZ 2,954,525

SINGLE PHASE WATTHOUR METER Filerd Jan. 16, 1958 3 SheetS-Sheet 1 INVENTOR.

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/zoMb/wZaf/n, @m v 9m Sept. 27 1960 F. KURZ SINGLE PHASE wATTHoUR METER Filed Jan. 1e, 195e 5 Sheets-Sheet 3 United States Patent die 2,954,525 Patented Sept. 27, 1960 SINGLE PHASE WATTHOUR METER Fred Kurz, Springield, lll., assignor, by mesne assignments, to Sangamo Electric Company, Springfield, Ill.,` a corporation of Delaware Filed Jan. 16, 1958, Ser. No. 709,223

6 Claims. (Cl. 324-137) The present invention relates to a single phase watthour meter, and is concerned primarily with providing a symmetrical magnetic circuit for fa single turn coil in the current circuit of such a meter.

ln the conventional type of watthour meter construction now in use, the magnetic path for the flux created by the current winding consists of a yoke provided with two legs, and to obtain satisfactory metering characteristics in this construction it has been necessary to divide the winding of each current circuit equally between these two core legs. For practical purposes of design in these meters, a maximum magneto-motive force of 400 ampere turns has been found to be most useable. Maximum current ratings ofltl, 20, or amperes result in numbers of turns in the current circuit coil or winding that work out satisfactorily yboth for 2 and 3 wire meters, and permits the building of symmetrical coils. In the case of a maximum current rating of 200 amperes, a one circuit, 2-turn, current coil for use on 2-wire service can be built symmetrically. However, in the case of 3-wire single phase service, where it is necessary to take two current circuits through the meter, this would allow only 1 turn to each circuit. In order to o-btain a symmetrical magnetic eld from each of these two circuits, it has been necessary to resort to such subterfuges and make-shift arrangements usually referred lto 'as split coils. These usually consist of two circuits in parallel attempting to divide the current in each circuit so that one-half of the total passes through a turn about each leg of the electro-magnet core. Such a coil is difficult and expensive to make, and the nal result often leaves much to be desired.

The primary .object of the present invention is to eliminate t-hese diiiiculties, and to provide a structure which will permit as little as one turn to be used symmetrically Vin the magnetic circuit.

This improved construction has resulted in shorter and simpler current windings, which can Ibe easily insulated and assembled with a amount of material.

Another object of the invention is to provide an im proved construction and relationship of the potential winding in the magnetic circuit. This improved construction has resulted in a potential winding characterized by a shorter mean length of turn than is practically Ifeasible with the older forms of construction. This advantage is attributable to the fact that the section of, magnetic core which passes through the-center of the potential coil passes the flux in one straight line throughout its length, thereby permitting the use of grain-oriented magnetic material, t

with a resulting smaller cross section of the core. Also,

the winding length being longer, there will be more turns per layer and hence fewer layers `for a given winding, making a coil which can be wound more rapidly and which will require less copper than in the present conventional potential coils.

A further advantage of this structure lies in the ease with which current coils can be assembled upon the magnetic structure. In the case of single turn coils, this `is not` so important since single turn coils usually have one side left open and can be threaded into place. However, in the case of multi-turn coils this feature is of prime importance.

Other objects, features and advantages of the invention will be apparent from the following detail description of one preferred embodiment thereof. In the accompanying drawings illustrating such embodiment:

Figure l is a rear view of my improved stator structure, showing the windings in section.

Figure Z is a fragmentary transverse sectional View taken at right angles to Figure 1, showing the meter disc in the stator gap.

Figure 3 is a view similar to Figure l, showing the represent-ative paths of the magnet-ic flux produced by the potential winding.

Figure 4 is a similar view showing typical paths of the magnetic flux produced by the ow of current in the current circuits.

Figure 5 is an elevational view illustrating the simplicity of the current coils with the improved stator structure.

Figure 6 is a diagrammatic View showing the prior conventional magnetic structure with the current coils in place, as used in present day watthour meters, and

Figure 7 is a diagrammatic perspective view showing the prior forms of coils only, as used in the conventional present day meter.

' The stator structure 10 of the meter embodies a potential electromagnet or core element 11 comprising two vertical side members 12, 12', which `are of identical laminated construction. The upper head portions 14, 14 of these side members are formed with dovetai1 shaped recesses 16, 16 for receiving the ldove-tail shaped ends f1S, 18 of the horizontally extending potential .magnet core 20. Mounted on this magnet core 20 is a horizontally extending potential coil 22. Extending inwardly from the side members 12, 12 below the potential coil 22 are horizontally extending arms 24, 24 which have their proximate or inner confronting ends separated by an air gap or by a non-magnetic spacer, either being alternatively indicated at 26. The rotor gap 28 is deiined directly below the horizontally extending arms 24, 24', the inner portions of these arms functioning as potential element polepieces for directing the passage of ilux across the rotor gap 28.

Mounted between downwardly extending legs 30, 30' of the laminated potential side members i2, 12 is the current coil core 32, also of laminated construction. This core 32 is of E-shaped outline comprising -a bottom cross bar portion 34 and two upwardly extending end legs 36, 36' and a center leg 38. The top ends or faces of these three legs 36, 36' and 38 define the underside of the rotor gap 28. The two upwardly extending end legs 36, 36 are spaced slightly inwardly from the downwardly extending outer legs 30, 30 of the potential core by air gaps or non-magnetic spacers 40, 40. The central leg 38 has a relatively deep vertical slot 42 formed transversely of its upper end. This slot 42 serves to divide the upper end of the central leg 38 into two spaced sub-legs 38aand 38h; and it also serves to receive the turns `44, 44 o-f a power factor compensation coil or winding to be later described.

Spanning the gaps between the upper ends of the center leg 38 and side legs 36, 36 are magnetic shunts 48, 48 which eifect overload compensation, as will belater described. These magnetic shunts comprise magnetic sheets `or laminations having `their ends spaced from contact with `56' for supporting the shunts.

Embracing or surrounding the center leg 38 are the current coils 66, 60 which have connection terminals 62, 62' (Figure 5) adapted for connection to prong term-inals or socket bayonets mounted on the meter' base. These current coils may be single turn or multi-turn, as will be later described, and have connection with two of the lines or circuits of a 3-Wire single phase service through the meter.

As shown in Figure 2, the vabove described stator structure acts on the conventional meter disc or rotor 64 which is mounted on a vertical spindle 66. tOne peripheral side or edge of the disc 64 rotates through the rotor gap 28, and the other peripheral side or edge of the disc has the usual arrangement of permanent damping magnets acting thereon. The spindle or shaft 66 drives the conventional dial registering pointers of the meter. As shown in Figure 2, the two turns or coils 44, 44 of the power factor compensating coil are connected in series and wound in opposite directions, and have connected in series therewith an adjustable resistance Wire 68 for adjusting the overall resistance in this circuit. These wind- .ings serve the purpose of adding a component of mag- Vterial. These grain-oriented materials are particularly effective in laminations which are so designed that the major flux path does not deviate materially from the rolling direction of the material. These materials are characterized by highly directional magnetic properties, that is, the core loss and permeability are much better parallel to the rolling direction than they are perpendicular to that direction. The use of grain-oriented material enables the core 2t) to be made of smaller cross-sectional area, which results in the potential winding 22 having a shorter mean length of turn than is-practically feasible in older forms of construction. Also, my new construction Ienables the core length and the winding length 22 to be longer resulting in more Vturns per layer and hence fewer layers for `a given winding, in consequence of which the coil 22 can be wound more rapidly and requires less copper than in present conventional potential coils. With the winding 22 assembled over the core 2t), this sub-assembly can then be inserted into the complete potential assembly 11 by forcing the dove-tail ends 18,18 into the dove-tail recesses 16, 16. The dove-tail ends 18, 18 may be horizontally slotted, as illustrated, to give them compressive resiliency in the act of being forced into the recesses 16, 16.

Figure 3 illustrates the representative paths throughout the entire stator structure of the magnetic flux produced by the potential winding 22, this potential flux being indicated by dotted lines. It will be seen that some of the potential ilux passes directly between the horizontally extending pole-piece arms 24, 24', some passes through the bottom cross bar portion 34 of current electromagnet 32, and some threads through the gap 28 and meter disc 64. This latter part of the potential flux, 'diagrammatically indicated at X, represents the useful pote-ntial flux which produces `eddy currents in the meter disc 64 to react with the ilux set up by the current coils 60, 60', and produces a iield which reacts with the eddy currents of the disc set up by the current iiux to produce the torque for driving the disc 64. This torque represents the useful part of the potential flux. It will be Vnoted that the provision of the slot 42 compels this flux X to pass in one direction through sub-leg 38a and to pass in the opposite direction through the other sub-leg 38h, reversing, of course, with each current alternation. Since the two turns or coils 44, 44 of the power factor compensation winding wound on these sub-legs 38a and 38h are wound in opposite directions, this potential flux X will generate an additive voltage in these two coils, thereby setting up a circulating current in this compensation Winding, depending upon the ilux linkage, the turns in the coils, and the resistanceg68 in this circuit. This current in the compensation winding in turn sets up a magnetic 4flux which adds vectorially to the potential flux, producing a resultant flux independent of the tlux produced by the current windings 60, 60. By changing the resistance 68 in this circuit, the current and hence the phase of the resultant flux can be changed, and this adjustment used `as the so-called power factor or quarter phasing adjustment. Y

Figure 4 illustrates the typical paths taken by the magnetic flux produced by the flow of current through the current coils 60, 60', the latter being connected with two lines or circuits of a 3-wire single phase service through the meter. The main path of this current flux, which is the useful current ilux, indicated by dash and dot lines in Figure 4, passes from both sub-legs 38a and 38b of the center leg 3S through the gap 28 and rotor disc 64 to the potential pole-piece arms 2 4, 24', and thence down through the side legs 36, 3G of the potential core 11 and across the air gaps 4t), 40 and back into the current core 32, the flux reversing, of course, with each current alternation. The current flux also flows through secondary paths defined by the magnetic shunts 48, 48', which bypass the rotor gap and disc. The proportion of ux flowing through these secondary paths depends upon the cross-sectional area of the shunts, the gaps 52 and the degree of saturation of the magnetic shunts. The single current core leg 38 affords a symmetrical core structure for the two current coils 60, 66. That portion of the potential flux cutting the disc 64 generates eddy currents therein, the magnetic fields of which react with the current flux to produce a torque in the disc about the shaft 66. Likewise, the current ilux cutting the disc 64 gencrates eddy currents therein, the magnetic fields of which react with the potential flux to produce torque in the disc.

Referring now to the overload compensating shunts 48, 48', the material and cross-section of these magnetic shunt plates, and the size of the gaps or non-magnetic spacers 52, 52', are so selected that the shunt plates will saturate at certain values of load current and produce in the meter so-called overload compensation as needed to overcomersuch retarding effects as current damping, and produce accurate registration at higher values of load currents. `One similar or exemplary embodiment of overload compensating means is disclosed in prior PatentV 1,727,509 issued September 10, 1929 to myself and Roscoe Wilmeth.

Figure 5 shows the simplicity in my improved meter of the two current coils 60, 60". In the case of a meter for 3-wire single phase service capable of carrying a maximum current rating of 200i amperes, if the accepted limitation of -a maximum magneto-motive force of approximately 400 ampere turns is to be adhered to, itis necessary that the two coils 60, 60' for taking the two curent circuits through the meter should not have more than one Y turn per coil. This is true of the coils 60, 60 in Figure 5V.

Herein each coil for each of the two circuits has only one i cross bar portion 34 of the current core 32, either fromV the front or rear side of the core structure. The connection terminals 62 can beY crossed over each other after the coil 60 has been threaded side-wise into place. Alternatively, the two coils 60, 60 can `be passedrdown over the top of the central leg 38 before the compensating shunts 48, 48 have been inserted into place. This latter mode of assembling the current coils 60, 60' is essential if lthese coils consist of more than one turn each, as would be true in the case of meters of lower current ratings. This latter mode of assembling multiple turn coils is a simple operation because the coils can be preformed and assembled over the central leg 38 before the mounting of the shunt 48, 48 and before joining with the potential core structure 11.

To further illustrate the contrast between my improved construction and Ithe conventional split-coil construction now prevalently in use, I have shown this conventional split-coil construction in Figures 6 and 7. For measuring 3-wire service, these prior current coils each consists of two split or separate parallel circuits 60a, 60h and 69'51, 60b. These split or parallel coils are shown as being mounted on a conventional, well-known stator structure comprising a vertically extending potential coil core leg 72 and to upwardly extending side by side current coil legs 74, 74. These divided current coils areconstructed and arranged so that the current in each circuit theoretically divides, with one-half of the current passing around each of the two current core legs 74, 74', in an effort to produce a field symmetrical with respect to the magnetic structure. The overall result is intended -to be equivalent to two single turn coils. Figure 7 shows the complication and diculty of preforming these split or dual coils before assembly. And after assembly the meter is subject to the previously described detrimental characteristics resulting from the use of .closed loop or short circuiting turns. All of this is avoided by my new construction.

It will be understood that my above described meter may be further provided with full load adjusting means, light load adjusting means, inductive load adjusting means, temperature compensating means, voltage variation compensating means, overload compensating means, etc., all of which are conventional in watthour meter practice.

While I have illustrated and described what I regard to be the preferred embodiment of the present invention, nevertheless it will be understood that such is merely exemplary and that numerous modications and rearrangements may be made therein without departing from the scope of the invention.

I claim:

l. In an inductive watthour meter forimetering 3-wire single phase service, the combination of a potential core structure, a current core structure, a rotor gap associated therewith, a meter disc revolving in said rotor gap, said potential core structure comprising two spaced downwardly extending side leg portions, dove-tail shaped recesses in the opposing faces of said side leg portions, a substantially horizontal core bar composed of grainoriented magnetic material, said core bar having dovetail shaped ends to t into said dove-tail shaped recesses of said side leg portions, a horizontally disposed potential winding on said horizontal core bar between said side leg portions, pole face arms extending inwardly from said side leg portions between said potential winding and said rotor gap, the inner ends of said pole face arms `being magnetically spaced from each other, said current core structure being of E-shaped outline comprising a lower cross bar portion having two outwardly disposed leg portions and a single centrally located leg portion extending upwardly from said lower cross bar portion, the outwardly disposed leg portions of said current core structure being disposed inside of and magnetically separated from the downwardly extending side leg portions of said potential core structure, two single turn current coils thre-aded laterally over said single centrally located leg portion and adapted for connection with two of the wires of said 3-wire single phase service, the upper end of said single centrally disposed leg portion terminating in a pole face at said rotor gap, a

substantially vertical slot extending 'down transversely through said single centrally disposed leg portion, a phasing winding having two oppositely wound coils passing through said slot, an adjustable resistance in series with said two oppositely wound coils, and szaturable magnetic shunts in bridging relation between the upper ends of the outwardly disposed leg portions and the single centrally disposed leg portion of said current core structure, said potential and current core structures establishing` a symmetrical magnetic circuit for the two single turn current coils concentrically threaded over said centrally disposed leg portion.

2. In an inductive watthour meter tor metering a 3- wire single phase service, the combination of a potential core structure, la current core structure, a rotor gap associated therewith, a meter disk revolving in said rotor gap, said potential core structure comprising two spaced downwardly extending side leg portions, dove-tail shaped recesses in the opposing faces of said side leg portions, a substantially horizontal core bar composed of grainoriented magnetic material, said core bar having dovetail shaped ends to t into said dove-tail shaped recesses of said side leg portions, a horizontally disposed potential winding on said horizontal core bar between said side leg portions, said current core structure comprising a single centrally disposed coil mounting coreV leg, and a plurality of current coils embracing said single coil mounting core leg and adapted for connection with diiiterent conductors of said 3-wire single phase service.

3. In a watthour meter, the combination of a potential core structure, a current core structure, a rotor gap aS- sociated therewith, a meter disk revolving in said rotor gap, said potential core structure comprising two spaced downwardly 'extending side leg portions, mounting recesses in the opposing faces of said side leg portions, a substantially horizontal core bar composed of grainoriented magnetic material, said core bar having mounting tongues projecting from opposite ends thereof to iit into said mounting recesses of said side leg portions, a horizontally disposed potential winding on said horizontal core bar between said side leg portions, said current core structure comprising a single centrally disposed coil mounting core leg, and a plurality of current coils embracing said Single coil mounting core leg and adapted for connection with diiferent lines of a supply service.

4. In a watthour meter for metering 3-wire, single phase service, the combination of a stator comprising a `potential core structure and a current core structure, a

rotor gap associated therewith, a meter disc revolving in said rotor gap, said potential core structure comprising an upper horizontally extending core bar, two downwardly extending side leg portions at the ends of said core bar, a horizontally disposed potential Winding on said horizontally extending core bar between said side leg portions, two pole face arms extending inwardly from said side leg portions between said potential winding and said rotor gap, the inner confronting ends of said pole face arms being magnetically separated from each other, said current core structure being of E-shaped outline comprising a lower cross bar portion having two outwardly disposed leg portions and a single centrally disposed leg portion extending upwardly frorn said lower cross bar portion, the two outwardly disposed leg portions of said current core structure being disposed inside of and magnetically separated from the two downwardly extending side leg p0rtions of said potential core structure, a plurality of current coils mounted concentrically on said single centrally disposed leg portion of said current core structure, the upper end of said single centrally disposed leg portion terminating in a pole face at said rotor gap, a substantially vertical slot extending down transversely through said single centrally disposed core leg dividing the pole face thereof into two sub-leg portions, each of which is in substantially vertical alignment with one of the inner confronting end portions of said pole face arms on the opposite side of said rotor gap, and a compensating winding extending -through said slot.

5. In a watthonr meter for metering 3-wire, single phase service, the combination of a stator comprising a potential core structure and a current core structure, a rotor gap associated therewith, a meter disc revolving in said rotor gap, said potential core structure comprising an upper horizontally extending core bar, two downwardly extending side leg portions at the ends of said horizontal bar portion, `a horizontally disposed potential winding on said horizontally extending core bar between said side leg portions, two pole face arms extending inwardly from `said side leg portions between said potential winding and said rotor gap, the inner confronting ends of said pole faceY arms having a magnetically separating gap therebetween, said current core structure being of E-shaped outline comprising a lower' cross bar portion having two outwardly disposed leg portions yand a single centrally disposed leg portion extending upwardly from said lower cross bar portion, the two outwardly disposed leg portions of said current core structure being disposed inside of and magnetically separated from the two downwardly extending side leg portions of said potenti-al core structure, a plurality of current coils mounted concentrically on said single centrally disposed leg portion of said current core structure, the upper end of said single centrally disposed leg portion terminating in a pole face at said rotor gap, a substantially vertical slot extending down transversely through said single centrally disposed core leg in substantially vertical alignment with the magnetically separating gap between the inner confronting ends of said pole face arms above said rotor gap, said vertical slot dividing the pole face thereof into two sub-leg portions each of which is in substantially vertical alignment with one of the inner confronting end portions of said pole facearms on the opposite side of said rotor gap,

-a power factor compensating winding having two oppositely wound series connected coils extending through said slot, and saturable overload compensating magnetic shunts disposed between the single centrally disposed core leg and the two outwardly disposed upwardly extending leg portions of said current core structure.

6. `In a` watthour meter for metering 3wire, single phase service, the combination of a stator comprising a potential Acore structure and a current core structure, a rotor gap assoicated therewith, a meter disc revolving in said rotor gap, said potential core structure comprising an upper horizontally extending core bar, two down- Wardly extending side leg portions at the ends of said core bar, a horizontally disposed potential winding on said horizontally extending core bar between said side leg portions, two pole face arms extending inwardly from said side leg portions between said potential winding and said rotor gap, the inner confronting ends of 4said pole face arms being magnetically separated from each other, said current core structure being of E-shaped outline comprising a lower cross bar portion having two outwardly disposed upwardly extending side leg portions and a single centrally disposed leg portion extending upwardly from said lower cross bar portion, the two downwardly extending side leg portions at the ends of Said core bar of the potential core structure extending in parallelfsideby-side lapping relation to the two outwardly disposed upwardly extending side leg portions of the current core structure, but being magnetically separated therefrom, a plurality of current coils mounted concentrically on said single centrally disposed leg portion of said current core structure, the upper end of said single centrally disposed leg portion terminating in a pole face at said rotor gap, a substantially vertical slot extending down transversely through Said single centrally disposed core leg dividing the pole face thereof into two sub-leg portions, each of which is in substantially vertical alignment with one of the inner confronting end portions of said pole face arms on the opposite side of said rotor gap, a compensating winding extending through said slot, and overload compensating magnetic shunts disposed between the ends of said outwardly disposed upwardly extending side leg portions and said centrally disposed leg of said current core structure, said shunts being magnetically spaced frornsaid current core structure and from said potential core structure and being of such composition and of such slze as to saturate at certain values of load current for effecting overload compensation.

References Cited in the le of this patent UNITED STATES PATENTS 

